Identification and Explanation of a Change in the Groundwater Regime using Time Series Analysis

Time series analysis is applied to identify and analyze a transition in the groundwater regime in the aquifer below the sand ridge of Salland in the Netherlands, where groundwater regime refers to the range of head variations throughout the seasons. Standard time series analysis revealed a discrepancy between modeled and observed heads in several piezometers indicating a possible change in the groundwater regime. A new time series modeling approach is developed to simulate the transition from the initial regime to the altered regime. The transition is modeled as a weighted sum of two responses, one representing the initial state of the system, the other representing the altered state. The inferred timing and magnitude of the change provided strong evidence that the transition was the result of significant dredging works that increased the river bed conductance of the main river draining the aquifer. The plausibility of this explanation is corroborated by an analytical model. This case study and the developed approach to identify a change in the groundwater regime are meant to stimulate a more systematic application of time series analysis to detect and understand changes in groundwater systems which may easily go unnoticed in groundwater flow modeling.     

Heli-borne gravity gradiometry in rugged terrain

For airborne gravity gradiometry in rugged terrain, helicopters offer a significant advantage over fixed-wing aircraft: their ability to maintain much lower ground clearances. Crucially, this provides both better signal-to-noise and better spatial resolution than is possible with a fixed-wing survey in the same terrain. Comparing surveys over gentle terrain at Margaret Lake, Canada, and over rugged terrain at Mount Aso, Japan, demonstrates that there is some loss of spatial resolution in the more rugged terrain. The slightly higher altitudes forced by rugged terrain make the requirements for terrain correction easier than for gentle terrain. Transforming the curvature gradients measured by the Falcon gravity gradiometer into gravity and the complete set of tensor components is done by a Fourier method over gentle terrain and an equivalent source method for rugged terrain. The Fourier method is perfectly stable and uses iterative padding to improve the accuracy of the longer wavelengths. The equivalent source method relies on a smooth model inversion, and the source distribution must be designed to suit the survey design.     

Mega-blowouts in Qinghai–Tibet Plateau: Morphology,distribution and initiation

Blowouts are wind-eroded landforms that are widely distributed in the north-eastern part in Qinghai–Tibet Plateau (QTP), China. These blowouts are thought to form in response to climate change and/or human activity but little is known about their morphodynamics. Using field surveys, remote sensing and geographic information system (GIS) spatial analysis, the distribution and morphology of blowouts are analysed and their initiation considered. Results show the QTP mega-blowouts are some of the largest in the world. The orientations of the trough shaped blowouts are parallel with the prevailing wind, but the saucer and bowl-shaped blowouts are influenced by bi-directional transport. Whilst regional patterns of blowout shape and size were observed to reflect the extent of aeolian sediments and wind regimes, the relationship between the different morphological parameters showed consistency. During initial stages of development, the length to width ratios of blowouts increase rapidly with area but after they reach a mega size this relationship stabilizes as blowouts widen. Initial luminescence dating shows that blowouts appear to have initiated ~100 to 500 years ago, coinciding with the Little Ice Age (LIA) climate event when northwest winds are known to have intensified. Further work is required to confirm this initiation period and establish the significance of mega blowouts for landscape degradation and human activities. © 2018 John Wiley & Sons, Ltd.     

A study case of bioluminescence potential dynamics in the Delaware Bay with observations and modeling

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New insights on the relative contributions of coastal processes and tectonics to shore platform development following the Kaikōura earthquake

We describe the immediate impact of the 14 November 2016 Kaikōura magnitude 7.8 (Mw) earthquake on shore platforms and cliffs around Kaikōura Peninsula. The earthquake caused an instantaneous uplift of ~1.01 m of the peninsula. We resurveyed seven profiles previously used for erosion monitoring and observed changes in the configuration of the shoreline. The coseismic uplift has fundamentally changed the process regime operating on the platforms and altered the future trajectory of shore platform and cliff development. Our observations highlight the interplay of waves, weathering, biology and tectonics. At this location tectonism strongly modulates the process regime, driving instantaneous changes in morphology and altering rates and patterns of erosion. Finally, the uplift of the Kaikōura coast has implications for changing resilience to climate change and sea level rise. Copyright © 2017 John Wiley & Sons, Ltd.     

Quantifying the effect of geomorphology on aeolian dust emission potential in northern China

Representation of dust sources remains a key challenge in quantifying the dust cycle and its environmental and climatic impacts. Direct measurements of dust fluxes from different landform types are useful in understanding the nature of dust emission and characterizing the dynamics of soil erodibility. In this study we used the PI-SWERL® instrument over a seasonal cycle to quantify the potential for PM₁₀ (particles with diameter ≤10 μm) emission from several typical landform types across the Tengger Desert and Mu Us Sandy Land, northern China. Our results indicate that sparse grasslands and coppice dunes showed relatively high emission potentials, with emitted fluxes ranging from 10⁻¹ to 10¹ mg m⁻² s⁻¹. These values were up to five times those emitted from sand dunes, and one to two orders of magnitude greater than the emissions from dry lake beds, stone pavements and dense grasslands. Generally, PM₁₀ emission fluxes were seen to peak in the spring months, with significant reductions in summer and autumn (by up to 95%), and in winter (by up to 98%). Variations in soil moisture were likely a primary controlling factor responsible for this seasonality in PM₁₀ emission. Our data provide a relative quantification of differences in dust emission potential from several key landform types. Such data allow for the evaluation of current dust source schemes proposed by prior researchers. Moreover, our data will allow improvements in properly characterizing the erodibility of dust source regions and hence refine the parameterization of dust emission in climate models. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Japan's earliest ostracods

Mesozoic, Cenozoic and especially Holocene ostracod faunas have been documented from Japan. Not surprisingly, considering the plate tectonic factors at play, very few ostracod faunas are known from its early Paleozoic successions. Our pilot studies have recovered new ostracod assemblages from early Paleozoic terranes of Japan. Acid preparation of carbonates has yielded low diversity, poorly preserved yet significant palaeocopid and podocopid ostracod faunas from Wenlock/Ludlow Series Silurian rocks at Gionyama in the Kurosegawa Terrane, Miyazaki Prefecture, Kyushu, and Hitoegane in the Hida‐Gaien Terrane, Gifu Prefecture, Honshu. The ostracod faunas include new eurychilinoid (Pauproles supparata gen. et sp. nov.), hollinoid (Hollinella orienta sp. nov.) and beyrichioid (Clintiella antifrigga sp. nov.) palaeocopid taxa. Conodonts recovered from the same sample as the ostracods from Gionyama confirm a mid‐Silurian age for the part of the Gionyama Formation in question. The ostracod faunas recovered from Gionyama and Hitoegane are the first confirmed, well‐documented record of the group from the Silurian of Japan and are therefore the earliest known ostracods from that country (a previous record of purported Ordovician ostracods from Japan is incorrect). The ostracod taxa display links with the paleocontinents of particularly Laurentia and Baltica and demonstrate a pan‐tropical signature; it appears that climate control was stronger than geographical control in shaping this pattern of ostracod distribution. The material recovered includes adult dimorphic (assumed sexual) pairs of three palaeocopid species, which represent Japan's oldest (423–433 million years) known ‘couples’.     

Quantifying erosional equilibrium across a slowly eroding,soil mantled landscape

The textbook concept of an equilibrium landscape, which posits that soil production and erosion are balanced and equal channel incision, is rarely quantified for natural systems. In contrast to mountainous, rapidly eroding terrain, low relief and slow-eroding landscapes are poorly studied despite being widespread and densely inhabited. We use three field sites along a climosequence in South Africa to quantify very slow (2-5 m/My) soil production rates that do not vary across hillslopes or with climate. We show these rates to be indistinguishable from spatially invariant catchment-average erosion rates while soil depth and chemical weathering increase strongly with rainfall across our sites. Our analyses imply landscape-scale equilibrium although the dominant means of denudation varies from physical weathering in dry climates to chemical weathering in wet climates. In the two wetter sites, chemical weathering is so significant that clay translocates both vertically in soil columns and horizontally down hillslope catenas, resulting in particle size variation and the accumulation of buried stone lines at the clay-rich depth. We infer hundred-thousand-year residence times of these stone lines and suggest that bioturbation by termites plays a key role in exhuming sediment into the mobile soil layer from significant depths below the clay layer. Our results suggest how tradeoffs in physical and chemical weathering, potentially modulated by biological processes, shape slowly eroding, equilibrium landscapes. © 2019 John Wiley & Sons, Ltd.     

Geomorphic process signatures reshaping sub-humid Mediterranean badlands: 2. Application to 5-year dataset

Badland landscapes exhibit high erosion rates and represent the main source of fine sediments in some catchments. Advances in high-resolution topographic methods allow analysis of topographic changes at high temporal and spatial scales. We apply the Mapping Geomorphic Processes in the Environment (MaGPiE) algorithm to infer the main geomorphic process signatures operating in two sub-humid badlands with contrasting morphometric attributes located in the Southern Pyrenees. By interrogating a 5-year dataset of seasonal and annual topographic changes, we examine the variability of geomorphic processes at multiple temporal scales. The magnitude of geomorphic processes is linked to landform attributes and meteorological variables. Morphometric differences between both adjacent badlands allow us to analyse the role of landform attributes in the main geomorphic process reshaping landscapes subjected to the same external forcing (i.e. rainfall and temperature). The dominant geomorphic process signatures observed in both badlands are different, despite their close proximity and the same rainfall and temperature regimes. Process signatures determining surface lowering in the gently sloping south-facing badland, characterized by lower connectivity and more vegetation cover, are driven by surface runoff-based processes, both diffuse (causing sheet washing) and concentrated (determining cutting and filling, rilling and gullying). The steeper, more connected north-facing slopes of the other badland are reshaped by means of gravitational processes, with mass wasting dominating topographic changes. In terms of processes determining surface raising, both mass wasting and cutting and filling are most frequently observed in both badlands. There is a clear near-balanced feedback between both surface-raising and -lowering processes that becomes unbalanced at larger temporal scales due to the thresholds overcome, as the volume associated with surface lowering becomes higher than that associated with raising-based processes. Rainfall variables control surface flow processes, while those variables associated with low temperature have a significant relation with mass movement-based processes and other localized processes such as regolith cohesion loss. Finally, our results point out that morphometry (slope and connectivity) together with vegetation cover are key factors determining geomorphic processes and associated topographic changes. © 2020 John Wiley & Sons, Ltd.     

Effective flood risk visualisation

Natural Hazards - The effective communication of flood risk offers the opportunity to ensure communities can adapt and respond appropriately to changing local conditions. At a time of diminishing...